The present invention relates to a system for reproducing a color image by means of a digitally fed printer and, more particularly, to a system that can scan an original image, present on a physical medium, and print multiple copies thereof by means of an independent digitally fed printer, such as a digital press.
Presently there are two major types of digital color image reproduction systems: One type is generally known as publishing system and may encompass many configurations and levels of operation; in one class of configurations it is known as color electronic prepress system (CEPS) and in another, widespread class it is known as desktop publishing system (DTP). The primary purpose of systems of this type is to digitally compose a ready-to-print image of one or more pages out of a variety of graphical elements, such as text, drawings and pictures. The graphical elements are fundamentally obtained from two types of sources--physical images and computer generated data. Source physical images are usually photographs (transparencies or opaque prints) but may sometimes also be press-printed pictures or drawings on physical media. Image elements from computer generated data range widely from text, through 2-D graphics, to renderings of 3-D objects. A typical DTP system is illustrated schematically in FIG. 1. Physical images are usually scanned by a scanner and converted to digital raster representation, in which form they are stored, alongside the data of the computer generated elements. Typically, each element is called up and possibly edited, using specialized application SW. In particular, raster images from physical sources may undergo various editing functions, which aim at improving, or even altering, the resultant image. Then, typically, the various elements are assembled together, by means of a page assembly application SW and under interactive control of an operator. The outcome of this is a page description file. One or more page description files are fed to a so-called raster-image processor (RIP), which outputs a complete output description file (or output file, for short) of a printed sheet in a raster format compatible with the printer to be used. Generally, any of a variety of printing devices may be used--from a desktop digital printer to a digital color press. The output file is fed to a print buffer in the printer or in the digital press, from where it is repeatedly fed to the printing engine to produce multiple copies of the sheet image. (More generally, such a file may also be fed to an imagesetter or a platesetter, to produce printing plates for conventional presses). Although the various processing functions may be carried out on a single computer, they are usually divided between a number of platforms, either because of the physical separation of the functions, due to practical workflow (which underlies the flexibility of DTP systems), or in order to maximize overall processing rate; in particular, the RIP function is often carried out in a dedicated platform--especially for high-quality or high-volume printing, such as is done in digital presses.
Sometimes, as is the situation underlying the present invention, a complete page image may already exist on a physical medium and it is desired to reproduce it, that is--to obtain printed copies thereof. In particular cases, such an image may consist of a single picture, which exists as a photographic print or transparency. A digital publishing system, as described hereabove, can be utilized for the purpose. However, since such a system is designed to carry out many more functions, it involves several stages of processing, as outlined above, which are interspersed with storage of files and require operator intervention to at least initiate, and possibly also control, each stage. Hence, its use for such a purpose is highly disadvantageous because--
(a) it is very costly and inefficient in terms of operator time and use of computer resources; PA1 (b) it takes a relatively long time to obtain a first copy; PA1 (c) it is prone to human errors--resulting in further prolongation of the time to first copy and/or in poor image quality. PA1 (a) lower printing speeds--typically three full-color copies per minute; PA1 (b) lower printed image quality (compared to most digital presses); PA1 (c) printing on a limited choice of media types--primarily medium-weight uncoated paper (in contrast to the variety of print media, including a large range of papers--from light uncoated to heavy coated and glossy, handled by digital presses); PA1 (d) construction as a compact office machine, for non-continuous operation, rather than for high volume production--which usually shortens MTBF and requires frequent service. PA1 --cause the scanner to scan the original images, PA1 --process resultant image data so as to obtain a complete digital representation of the page image, the representation being stored in the processor at most once, PA1 --cause the representation to be transferred to the printer in a raster format that corresponds to the print raster, separated by printing colors, and PA1 --cause the printer to print the page image, PA1 cause the scanner to prescan the original image, PA1 display on the image display means a preview image resulting from the prescanning, PA1 enable an operator to set or modify some or any of the parameters interactively with the preview image, to result in modified parameter values, and PA1 cause the modified parameter values to take effect when subsequently governing scanning and image processing,
The other major type of digital color image reproduction system is represented by so-called color copiers. A typical color copier is schematically illustrated in the block diagram of FIG. 2. It consists primarily of a scanner, an image processor, an image buffer memory and a printer. The original image-carrying medium is scanned by the scanner, the resulting digital image data is processed, so as to optimize the image and to convert the color components, then fed through the buffer memory to the printer. Operation of a copier is largely automatic and is internally controlled (e.g. by the controller block in the illustration)--possibly according to parameters input by an operator through a user interface. Characteristically, all the HW components are housed in a single unit and the printer is the exclusive printing device. Also characteristically, the printer is matched to the scanner in scan-line frequency (typically 300-400 LPI) and in operational speed (since, in most cases, only a single copy or a very small number of copies is made from each original).
Color copiers are inherently suitable for carrying out reproduction of a physical page image (which is the subject of the present invention), overcoming the disadvantages, enumerated above, of using a publishing system for the purpose. However, they have several disadvantages, when compared to using a publishing system in conjunction with a typical digital press, some or all of which may be significant in particular practical cases, namely--
In certain types of business locations where the need for a physical image reproduction system could arise, there may already be a digital color printer, such as a typical office printer, installed. Such a printer would normally serve to print images prepared in a publishing system (as described above). As pointed out, the use of the entire publishing system for the sole purpose of reproducing a physical image would be uneconomical and unsatisfactory. On the other hand, purchasing a copier for this purpose, in addition to the installed system, could also be uneconomical, since a copier includes both a scanner and a printer--two relatively costly components, while the printer is, in effect, superfluous. It would, in such a case be more economical to have a system available that includes only a scanner and the necessary image processor, which would utilize the existing printer to print copies, especially if the latter is not utilized all the time, as is the typical case. This is particularly true for color reproduction, since the prices of color copiers are relatively high. It may be argued that in such situations, the lower quality and speed of office printers (as compared to digital presses) may be acceptable for copying, as they are for publishing, and thus the relative disadvantages of office copiers (over the use of the combination of publishing system and digital press), mentioned above, are no longer valid. However, in these very situations, their inherent economic disadvantages, just discussed, may become of paramount consideration. It may be of note that similar economic considerations have already to led to an inverse solution, suitable for other business situations, namely: A copier is made to also function as an output printer, by attaching a suitable RIP, which is fed from a DTP.
There is thus a widely recognized need for, and it would be highly advantageous to have, a system that enables quickly, reliably and economically producing quality copies of a physical color image, utilizing an available digital printer or digital press.